DEVELOPMENT OF EGGS AND YOLK-SAG LARVAE OF 



YELLOWFIN MENHADEN 



By John W. Reintjes, Fishery Research Biologist 

 Bureau of Commercial Fisheries 



The menhadens, genus Brevoortia, inhabit the 

 coastal waters of the western Atlantic Ocean from 

 Nova Scotia to central Argentina and support the 

 largest commercial fishery in the United States, 

 yet their early developmental stages are little 

 known. Kuntz and Radcliffe (1917) described de- 

 veloping eggs, yolk-sac larvae, and older larvae 

 identified as Atlantic menhaden (B. fyrannus). 

 Based on their descriptions, Atlantic menhaden 

 eggs and larvae have been reported from Chesa- 

 peake Bay (Pearson, 1941), Long Island Sound 

 (Perlmutter, 1939; Wheatland, 1956; Richards, 

 1959), and Narragansett Bay (Herman, 1959). 

 Eggs, tentatively identified as Atlantic menhaden, 

 were obtained off the North Carolina coast in No- 

 vember and December, 1956 and 1957 (Reintjes).' 

 In 1957 eggs were hatched in the laborator_v, but 

 the larvae died after the yolk sac was absorbed. 



Menhaden eggs and larvae were reported from 

 plankton collections made off the south Atlantic 

 coast of the United States during three cruises of 

 the motorsliip Theodore N. Gill (Reintjes, 1961), 

 but no identification to species was made. Al- 

 though the foregoing observations provided a de- 

 scription of eggs and larvae and information on 

 their distribution, some question remained as to 

 whether these actually were menhaden. 



The absence of spawning, or running-ripe, fish 

 in the landings has precluded mechanical fertiliza- 

 tion and rearing of the eggs and yolk-sac larvae 

 for the identification of Atlantic menhaden (B. 

 tyrannus) and Gulf menhaden (B. patronus), the 

 two species of principal commercial importance. 

 The occurrence of spawning yellowfin menhaden 

 (B. smithi) in the landings of a gill-net fishery at 

 Sebastian, Fla., made possible the distinction of 

 eggs and yolk-sac larvae of this species from those 



' Egps and yolk-sac larvae of Atlantic menhaden. Unpublished manu- 

 script. V.S. Bureau of Commercial Fisheries Bioloeical Laboratory, Beau- 

 fort, N.r. 



NOTE.— Approved for publication June 2S, 1901. Fishery Bulletin 202. 



of other clupeoid fishes. Development of embryos 

 and larvae was followed and described from the 

 time of fertilization untU absorption of the yolk. 

 The procedures of the work were: (1) obtain 

 ripe ova and sperm from freshly caught yellowfin 

 menhaden, (2) effect fertilization by mixing the 

 sex products, (3) hold fertilized eggs in a suitable 

 environment at known temperature during devel- 

 opment, (4) remove and preserve examples of de- 

 veloping eggs and larvae, (5) observe the proper- 

 ties of eggs and the behavior of early larvae, and 

 (6) collect planktonic eggs and larvae concurrently 

 for comparative material. 



MATERIALS AND METHODS 



Beginning in November 1959 weekly samples of 

 adult yellowfin menhaden were obtained from gill- 

 net landings at Sebastian, Fla., to follow matura- 

 tion of ovaries and testes. Each sample consisted 

 of about 100 fish taken at random from the catch. 

 Free-flowing milt was observed from cut testes in 

 mid-December, and on January 11, 1960, several 

 females in the sample extruded ova when pressed 

 firmly. Each week thereafter, the number of fish 

 apparently ready to spawn increased. On Febru- 

 ary 8, approximately one-fourth of the females 

 and all of the males appeared ready to spawn. 



On February 12, a temporary field laboratory 

 was set up in a small dockside building at Sebas- 

 tian, Fla. Ecjuipment included compound and 

 dissecting microscopes, thermometers, salinom- 

 eters, small dip nets, one-half-meter plankton 

 nets, an assortment of glass preparation bowls 

 and polyethylene containers, and pens with nylon- 

 net compartments. Other than the pens, no 

 other equipment of special construction was used. 



For rearing purposes, two pens, or enclosures, 

 were constructed, following the design of the blue 

 crab shedding floats, or live-cars, used throughout 

 the Chesapeake Ba.y and middle Atlantic region 



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